1. Field of the Invention
The invention relates to a composite reinforced fiber for high G loads and more particularly to an optical fiber reinforced with a woven intermediate layer covered by a metal sheathing.
2. Description of Related Art
The invention defines a reinforced optical fiber particularly suited for battlefield use with a mortar or cannon fired projectile. Such a battlefield system is described in U.S. Pat. No. 4,770,370 to Pinson.
Although reinforced coatings for optical fibers are known, none are currently available that possess the necessary strength and flexibility that permit the fiber to be used in a mortar or cannon launched munition and survive the handling and environment associated with an active battlefield. Special fiber attributes are required for (1) the fiber extending from the mortar to the projectile controller, (2) the fiber extending from the mortar to the fiber pay-out bobbin, and (3) the transition between reinforced fiber and unreinforced fiber wound on the bobbin.
The method for the fabrication of the reinforced fiber that will be used as the core for the present invention is defined in U.S. Pat. No. 4,886,562 assigned to the assignee hereof which defines the method for weaving a central strand of optical fiber in a woven or plaited coating of glass or other suitable high strength flexible material.
It has been found that in the vicinity of the mortar, two types of damaging environments exist. The first is human induced. In this case, the soldier is in a life threatening situation where optical fibers are strewn on the ground. The fiber may be stepped on, pulled, bent or otherwise manhandled. The second damaging environment is caused by the high G loads created during launch. In these environments, it has been found that a metal reinforced fiber is desirable for protection.
Metal sheathed optical fiber is known in the telecommunication field as described in U.S. Pat. Nos. 4,361,381 to Williams and 4,396,446 to Franken. However, the prior art of metal sheathing of optical fiber does not provide metal sheathing which is suitable for the above-described environment.
Methods of sheathing a metal wire in metal casing are known in the art as shown in U.S. Pat. No. Re. 28,961 to Tsukamoto. However, these methods do not provide for the control of tension on the optical fiber that is provided by the present invention. Additionally, U.S. Pat. No. 4,270,963 to Howet discloses an apparatus for wrapping metal foil around an optical fiber, but does not provide the smooth progressive curling and shaping of the present invention.